Slurried blasting explosive containing as sensitizing ingredient liquid non-explosive alkyl nitrate

ABSTRACT

THIS INVENTION RELATES TO AN IMPROVED BLASTING EXPLOSIVE OF THE KIND KNOWN AS SLURRIED EXPLOSIVE WHEREIN A WATERSOLUBLE OXIDISING SALT AND FUEL ARE SUSPENDED IN AN AQUEOUS MEDIUM CONTAINING AS A SENSITIZING INGREDIENT, A LIQUID NON-EXPLOSIVE ORGANIC NITRATE, I.E., ISOPROPYL NITRATE OR AMYL NITRATE.

3,681,156 SLURRIED BLASTING EXPLOSIVE CONTAINING AS SENSITIZING INGREDIENT LIQUID NON- EXPLOSIVE ALKYL NITRATE William Dick, Stevenston, and Owen Allen Gurton,

Fairlie, Scotland, assignors to Imperial Chemical Industries Limited, London, England No Drawing. Continuation of application Ser. No. 815,504, Apr. 11, 1969. This application Feb. 10, 1970, Ser. No. 9,122 Claims priority, application Great Britain, Apr. 22, 1968, 18,831/68 Int. Cl. C06b 15/00 U.S. Cl. 149-22 15 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved blasting explosive of the kind known as slurried explosive wherein a water- .soluble oxidising salt and fuel are suspended in an aqueous medium containing as a sensitizing ingredient, a liquid non-explosive organic nitrate, i.e., isopropyl nitrate or amyl nitrate.

This is a continuation of application Ser. No. 815,504, filed Apr. 11, 1969, now abandoned.

Slurried explosives for use in large diameter shotholes, for example greater than 4" diameter, need not generally contain a self-explosive ingredient, but for slurried explosives having a specific gravity more than 1.3 for use in narrower shotholes it is usual, in order to avoid propagation failures, to include in the composition a self-explosive sensitising ingredient, for example TNT, PETN, cyclotrimethylenetrinitramine or nitroglycerine. The inclusion of such a self-explosive ingredient renders the composition less safe to store and handle because of its increased sensitivity to ignition by impact or friction.

It is an object of this invention to provide a slurried blasting explosive sensitised by a non-self-explosive ingredient.

In accordance with this invention a slurried blasting explosive as hereinbefore defined contains, as a sensitising ingredient, a liquid non-explosive organic nitrate. Preferred organic nitrates include isopropyl nitrate and amyl nitrate. In addition to improving the sensitivity of the explosive compositions and so enabling them to be more readily initiated and fired in smaller diameters without propagation failures, the inclusion of these organic nitrates reduces the degree of aeration in the mixing of the composition, thereby enabling compositions of higher density to be prepared. The organic nitrates also tend to prevent the slurried explosives sticking to plastic containers. Slurried explosives in accordance with the invention may readily be prepared which will propagate in narrow shotholes 4) even at specific gravities greater than 1.3.

Preferably the slurried explosive of the invention comprises 2 to 25% by weight of the liquid organic nitrate.

The explosive composition preferably comprises, as oxidising salt, nitrate of ammonia, sodium, barium, potassium or calcium or a mixture of such nitrates. Advantageously the composition comprises a mixture of ammonium nitrate and sodium nitrate containing at least 50% by Weight of ammonium nitrate. The fuel conveniently comprises carbon, fuel oil, carbohydrate, for example sugar, metal or metalloid, for example aluminium, magnesium, boron or silicon, water-soluble lignosulphonate or mixtures of these fuels.

In order to prevent segregation of the ingredients it is advantageous to include in the slurried explosive a thickening agent, for example a water-soluble polysaccharide such as guar gum to thicken the water, or nitrocellulose 3,681,156 Patented Aug. 1, 1972 to thicken the organic nitrate. When nitrocellulose is pres cut its rate of gelation may be increased by incorporating ethyl alcohol into the composition.

The explosive may, if desired, comprise a cross-linking agent, for example zinc chromate or sodium borate, to crosslink the polysaccharide.

The preferred slurried blasting explosive of the invention comprises (by weight) 50-85% ammonium nitrate, up to 15% sodium nitrate, up to 15 aluminium, up to 5% non-metallic fuel, 0.2-2.0% guar gum, 5-25% water and 225 isopropyl nitrate or amyl nitrate.

The invention is further illustrated by the following examples in which all percentages are by weight.

EXAMPLES 1 TO 8 Details of the compositions and the properties of the slurried explosive composition of the examples are given in the table.

In preparing the explosives the solid ingredients were first mixed and the liquids were then added and stirred into the mixture except that in Examples 6 and 7 the isopropyl nitrate and alcohol were first thickened with the nitrocellulose and the thickened mixture added to a mixture of the other ingredients.

The velocity of detonation when confined was determined on a charge of explosive filling a mild steep pipe 1 /2" diameter x wall thickness or 3" diameter x 4" wall thickness detonated by a 30 g. Pentolite (50/50 TNT/PETN) primer. The velocity of detonation when unconfined was determined on a charge of explosive filling a 3%" diameter tube of polyethylene film detonated by a 225 g. Pentolite primer.

The specific gravity of a slurried explosive of the same composition as Example 1 except that the isopropyl nitrate was replaced by sugar was 1.20.

TABLE Example number 1 2 3 4 5 6 7 8 Composition, percent:

Ammoniumnitrate. 68.0 62.0 68.0 70.0 64.5 63.2 58.2 64.3 Sodiumnitrete 5.0 10.0 5.0 8.0 10.0 5.0 5.0 5.0 Aluminium ..10.0 10.0 10.0 10.0 10.0

Nitrocellulose Alcohol (industrial methylated We claim:

1. A slurried blasting explosive composition wherein a water-soluble inorganic oxidizer salt and a fuel are suspended in an aqueous medium containing as a sensitizing ingredient, a liquid non-explosive alkyl nitrate of from 3-5 carbons.

2. An explosive as claimed in claim 1 wherein the nitrate is selected from the group consisting of isopropyl nitrate and amyl nitrate.

3. An explosive as claimed in claim 1 comprising 2 to 25% by weight of said liquid organic nitrate.

4. An explosive as claimed in claim 1 wherein said oxidizer salt is selected from the group consisting of ammonium nitrate, sodium nitrate, barium nitrate, potassium nitrate, calcium nitrate, and mixtures thereof.

5. An explosive as claimed in claim 1 wherein the oxidizer salt is a mixture of ammonium nitrate and sodium nitrate containing at least 50% by weight of ammonium nitrate.

6. An explosive as claimed in claim 1 wherein said fuel is selected from the group consisting of carbon, fuel oil, carbohydrate, metal, metalloid, water-soluble lignosulphon'ate and mixtures of these fuels.

7. An explosive as claimed in claim 1 wherein said fuel is selected from the group consisting of sugar, aluminium, magnesium, boron and silicon.

8. An explosive as claimed in claim 1 comprising a thickening agent.

9. An explosive as claimed in claim 8 wherein the thickening agent comprises Water-soluble polysaccharide.

10. An explosive as claimed in claim 9 comprising a cross-linking agent to cross-link the polysaccharide.

11. An explosive as claimed in claim 10 wherein the cross-linking agent comprises zinc chromate or sodium borate.

12. An explosive as claimed in claim 9 wherein the water-soluble polysaccharide comprises guar gum.

13. An explosive as claimed in claim 8 comprising as thickening agent, nitrocellulose.

14. An explosive as claimed in claim 13 comprising ethyl alcohol to increase the rate of gelation of the nitrocellulose.

15. A slurried blasting explosive as claimed in claim 1 comprising (by weight) 50 to 85% ammonium nitrate, up to 15% sodium nitrate, up to 15% aluminium, up to 5% non-metallic fuel, 0.2 to 2.0% guar gum, 5 to 25% of water and 2 to 25% isopropyl nitrate or amyl nitrate.

References Cited UNITED STATES PATENTS l0/l967 Smiley l4988 X 4/1968 Stiefel et al l4988 US. Cl. X.R. 

